Various types of fasteners are used to engage implants and other devices to bone. In the spinal field, bone screws are commonly used to attach plates, rods and other types of implants and devices to one or more vertebrae. Many existing bone screws include a threaded shank portion adapted for engagement in bone, and a head portion for coupling to an elongate member such as a spinal rod via a connector mechanism. The threaded shank portion of the bone screw typically includes a single, constant pitch threading having a constant and uniform flank and flank angle suitable for engagement or purchase of cancellous bone. However, conventional bone screw threadings are not particularly suitable for engagement or purchase of different types or regions of bone, such as the cancellous and cortical regions of bone, and also do not lend to providing increased support and stability to the bone screw when driven into bone.
There remains a need for an improved bone screw. The present invention satisfies this need and provides other benefits and advantages in a novel and unobvious manner.